Heterogeneous nucleation in an aluminum droplet at low supercooling

Abstract The crystallization of the aluminum (Al) sample was detected by the differential scanning calorimetry (DSC) at the undercooling Δ T C ∼ 18.3°C. At the undercooling Δ T = 6.8°C < Δ T C , the crystallization event was detected after a time delay of several minutes. The nucleation kinetics on an inner droplet surface is analyzed by numerically solving of the nucleation equations to determine the number of nuclei formed in the Al droplet sample of the mass m 0 = 9.91 mg at Δ T = 6.8 °C. The depletion of the Al melt due to the formation of crystal nuclei is taken into account. The nucleation rate for different cluster sizes tends to a quasi-stationary limit which is lower than predicted by the classical nucleation model. Homogeneous nuclei in the droplet volume are formed earlier than heterogeneous ones, but at longer times (several minutes) the heterogeneous nucleation prevails.